Over the years, the world of home entertainment has changed dramatically. Today most U.S. households have a large color television with at least 50 viewing channels and a VCR or DVD. More and more people are adding additional audio components to their entertainment center to create home theater systems. The world of home theater is evolving and consumers have a wide range of options, particularly in the area of available speakers for producing the most theater-like sound within the home entertainment environment.
Speakers for use with home theater systems preferably reproduce all frequencies that the soundtrack delivers. Typically, this is considered to extend from about 20 hertz (cycles per second, also Hz) to 20 kilohertz (thousand cycles per second, also kHz). However, reproduction of this full range of frequencies is difficult, especially when the left, center, right and surround speakers are small in size. Speakers typically include one or more speaker drivers, each of which is capable of reproducing a certain range of frequencies. The basic types of speaker drivers are generally referred to as woofers, midrange drivers and tweeter (high frequency) drivers. It is important to note that to produce linear sound over a wide range of frequencies, you can break up the audio frequency range into several smaller sections that are each reproduced by one of these specialized drivers.
Woofers are physically the largest drivers and are designed to reproduce low frequency sounds, for example in subwoofers, those sounds occurring below 100 Hz. Next are the midrange drivers that are designed to reproduce a range of frequencies that extend typically between 200 Hz and as high as 5 kHz. To round out the array, the smallest of the drivers are the tweeter drivers. Because of their small size, the tweeters are better able to reproduce higher frequencies than midrange drivers.
From this, one may conclude that there is an optimum size for a driver depending upon the frequency range it is intended to reproduce. To produce high frequency sounds, which have shorter wavelengths, the speaker diaphragm must vibrate more quickly. Conversely, it is difficult for small drivers to move enough air to produce very low frequency sounds because of the small radiating area. To provide a speaker system that reproduces a wide range of frequencies, multiple drivers are typically used, often sharing a common enclosure.
It is well accepted that to achieve the best overall sound quality from a speaker system, it is important to ensure that such a system includes speakers designed to function together to produce a linear response throughout the entire audio bandwidth. However, in this light, an optimal speaker system may not be readily attainable or practical when considering factors such as size, cost and consumer appeal.
One traditional approach to providing full range sound while limiting the size of the front, left, right and rear surround speakers is to use a subwoofer. A subwoofer, which is a speaker having one or more woofer drivers, is typically used to reproduce low frequencies, typically only frequencies below 100 Hz. A subwoofer may be used without interfering with the imaging of the speaker system, because we hear low frequency sounds as non-directional. Satellite speakers are then used in various positions, such as front left and right, and for the rear surround speakers. These satellites may be smaller since they are not required to produce low frequency sound. Instead, they produce higher frequency sounds, which we perceive as being directional. These satellite speakers typically include only a small woofer, and midrange and/or tweeter drivers. The use of smaller drivers allows the satellites to be smaller than a “full range” speaker. The smaller the satellite, typically the higher the bass cutoff frequency.
The problem that remains herein is that small satellite speakers using 3½ inch or smaller woofers cannot reproduce low distortion sound pressure levels of above 100 db at frequencies as low as 100 Hz, the recommended highest crossover frequency to subwoofers for most surround sound systems. An added problem is that most surround sound receivers do not permit the option of extending the upper frequency cutoff of the subwoofer to above 100 Hz. The present invention seeks to provide a new technological approach that would in effect create a “bridge” between the subwoofer and the small satellite speakers to improve the overall audio quality of the surround sound speaker system.